Non-Occupant Borrower
A parent or other co-borrower does not necessarily have to live in the home to help a primary-residence borrower qualify.
Fannie
Fannie permits non-occupant borrowers on purchase, limited cash-out and cash-out refinance transactions, subject to borrower and transaction requirements. A non-occupant borrower signs the note and has joint liability but does not occupy the subject property.
Occupancy
For a standard Fannie principal-residence transaction with multiple borrowers, generally only one borrower must occupy and take title unless another product rule imposes a stricter requirement.
Official agency baseline
Fannie Mae Selling Guide · Freddie Mac Seller/Servicer Guide
These are agency-level rules. AUS findings, mortgage insurance, product restrictions and lender/investor overlays can still affect a real loan.